LU81989A1 - INDUSTRIAL PROCESS FOR THE SEMI-CONTINUOUS MANUFACTURE OF ZEOLITE A - Google Patents

Description

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The present invention çcncerr.e uns industrial preparation c't zialiihe A salon a sami-continuous process.

The applications of zeolites are based on their; well known properties of cation exchangers, described by example 5 in the •• Comprehensive treatise on incrganic end theerc-: | ticol chemistry ”from J.W, MELLQR vol. VI, part 2, Longman Editors | 1925, p. 575-579, and in particular on the possibility of exchanging I the forgotten sodium atoms contain for calcium ions, j 1 I The most used of the zeolites is the zeolite A, of!

j MO formula Na-pO, ^ -2 ^ 3 * ^ 5x0 ^,> '° ù x can vary from 1 to B

I depending on the drying conditions of the product, the h most used products corresponding to è x - 4 to 5.

J <· To promote the exchange capacities of Ca ++ and the selectivity of the zeolite, this must be the purest possible; 15 ble and therefore be well crystallized, any impurity can be either inactive or less selective.

it ^ I Finally, when this zeoiiths is incorporated into a! detergent, it is essential that the particle size distribution; it is tightened around a median diameter of 2 b 5 microns, suffi-Ι 20 are small enough to avoid retention of the product in textile fibers, but sufficient to allow separation ; easy solid / liquid during manufacturing.

, The synthesis and the ion exchange properties of zeoj p, synthetic lithes and in particular of zeolite A are good I 25. known for many years (see "Ion exchange" '' by Friedrich Helfferich, 1962, Mc Graw - Hill Book Company, Cha-j J pitre 2, pages 10-16).

The synthesis processes are all carried out batchwise by mixing the elements Si, Al and Na brought in various forms, forming a silicoaluminate gel which precedes i; pite. This gel is then crystallized from zeolite A by ripening in the mother liquor containing an amount of free soda and soluble alumina compatible with the type of zeolite obtained. Such are the methods described for example in US patents 2,841,471 and 2.B47.2B0, the B.F. 1.404.467, the B.E. B13.5B1 and the DAS 2.517.21 B.

This intermittent precipitation leads to variations ”

Lions imoortantes of the contents in Na-, / -3, -0 and Li-O-, of in 3 5cunur ’this J t-‘ 5.3nua of the mixture. IX results in a significant K terogeneity-S of the product obtained from the point of view of particle size, crystal.!. Inite and; exchange selectivity (size of pr; es). ! 5 A completely continuous manufacturing process, claimed by the company CHEMICAL PRODUCTS ci ICE KU HLM Ai H “'in patent application No. 77 * 23373 allows the preparation of La silicoaluminate gel. mixture of constant composition, but has the disadvantage of requiring a relatively large number of ripening tanks arranged in cascade to avoid the short-circuiting of a certain proportion of freshly precipitated gel and thus obtain the desired particle size.

Continuing its work in this field, the applicant 15 has discovered and perfected a process for the manufacture of zec-lithe which overcomes the various difficulties encountered. This process consists in preparing, by instantaneous precipitation, a Na silicoaluminate gel from solutions of La silicate and Na aluminate, mixed simultaneously and continuously, by means of a suitable apparatus. The quality of the production ’of this continuous mixing depends on the quality of the product obtained.

Indeed, this mixing must be carried out quickly And be of such an efficiency that there is at no time a localized excess j of silica compared to the alumina (one must have number; 25 of moles A1_, 0_ 2 moles Si0o). Such an excess of silica, even, v 2 3- "· c 7!

momentary, would degrade the quality of the product; by initiating precipitation and crystallization of a silico- | aluminate other than zeolite A, J

The mixing is carried out continuously in a reactor provided with a stirring system allowing perfect and instantaneous homogenization such as a turbine or any other suitable means.

The capacity of this reactor is calculated to obtain a time of; average stay between 30 seconds and 20 minutes essential to ensure complete gel formation.

35 The supply of the two reaction solutions, the flow rates of which are regulated, takes place in the zone of strong suction created by the turbine. The action of this turbine is further increased i f · 3 i

'I

: '* if we place this in a fixed saucer, it will turn in turn .-. îî as long as it. : 5 "'| 1. This saucer is made up of two trays, the | concavity is directed towards the turbine, These two trays cloi-! 5 sound a volume into which the two reaction solutions are injected or aspirated.

The silicoalinninate gel of Na thus prepared continuously, is transferred by overflow into a second reactor, equipped with a stirring system, and maintained at constant temperatures in a range q of 75 5 1DD ° C to allow crystallization , 'of the 2nd A desired. This crystallization ss is thus done in discontinuous i, which has the advantage of being able to adjust at will the desired degree of crystallinity and the particle size of the product: 1 final by acting respectively on the duration of ripening and the,

T 5 agitation conditions. I

i ^ The continuous preparation of the silicoaluminste gel of, 'ί; Na can Wax made from, on the one hand, this solutions of elu-! | sodium minate characterized by a molecular rspoort

I A12D ^ H-0 I

j ................. between 0.3 and 0.8, and A ratio · —.....-- between I

j, Na2ü ’Na20 j:! 20 between 5 and 150, the said solutions being obtainable, either i by attacking alumina hydrated with a sodium hydroxide solution, or taken from a Bayer cycle for the manufacture of alumina, and on the other hand, from solutions sodium silicate characterized by a 1 '' SiO! - v molecular ratio 2 between 2 and 3.5 and a ratio; 'i. 'H20 Na20! ï 25 between 25 and 100, said solutions can be j * 2 * | prepared from variable raw materials silica and soda: according to economic criteria, either sodium silicate powder 1; ii industrial, knows industrial sodium silicate detergents, I 1 is silica contained in sands and soda, or soda and 3Q silica gel recovered from fluosilicic acid residue from a workshop for the manufacture of aluminum fluoride or hydrofluoric acid, or the treatment of gar released during the treatment of natural phosphates, or sodium silicate from a bauxite desilicate workshop before treatment in J's factories! ! t alumina fabricotion, either in the residueiri 3 chte-'uc. 1 or do the manufacture of aluminum salts by attack by wet can of natural silicoalumines such as kaolin or clays, either: silica obtained thermally, for example during fobri-5 cations of magnesium, silicon-metal, or silicon alloys; . The mixture resulting from the addition of these aluminate and silicate solutions of A must have a molecular ratio 2 2 3 3 CD CDHipris between 0.5 and 1 2 2 and the content of a a a O 5i02 be adjusted for fear that the sodium hydroxide concentration of the liquor 10 * in which, after precipitation, this crystallization is carried out, is not greater than 135 g / 1 of MaOK, to avoid the crystallization of silicoaluminae of the inactive feldspathoxd type, months is not less than 25 g / l of LaCH so that the rate of crystallization of zeolite A is compatible with industrial production. After ripening of the sodium siiicoaluminate gel prepared as described above, a suspension of crystallized zeolite A is obtained which is separated from its mother liquors by any suitable solid / liquid separation means (decantation, filtration, etc.) then washed and dried, j The zeolite A produced by the process described above has the following characteristics: tight particle size distribution, 90% of the j; ! j i. | [! grains in a range of 4 μ for a median diameter j ^ of between 1 and 1D P adjustable according to use | 25 planned. j - ion exchange capacity greater than 110 mc j

++ / I

Ca / g of dry product,

Zeolite A thus obtained is particularly suitable for use in detergents to soften hard water. The following examples illustrate the invention without any- '. times limit it * 'EXAMPLE 1.

By attack at 100 ° of alumina hydrated with a sodium hydroxide solution, a solution A of sodium aluminate containing 35 54.3 g of A ^ Qj and 81.1 g of Na2O per liter is prepared (ie ai2o3 ratios h2o and ——— respectively 0.40 and 42).

Na20 Na20 i "» • · ρ, -Λ ;;. = Olution o ^ rs l ^ ou do s 1 i ca te de Ma en poudra indusio here, we prepare a solution 3 this silicate of Ma containing i 137, 4 g 3e ΰίΟτ and 47 ”2 q in liter (let back relate to 5i O, H? 0 j | cr respectively of 3 and 69), j ί N-3 -. 0 V.3-p0 | £ 4

S

j 5 We prepare a gel in si.13ccaluoinate of Ma having a | ratio of 0f6 by simultaneously sending, to the temperature tun 5i02 c! e 90 ° Cf 0 (E6 1 in solution A and 0 * 344 1 in solution B in a reactor of the type described above * and whose volume has been calculated to obtain a residence time of only 45 seconds * The bottom lg thus obtained is transferred by overflowing into the ripening reactor. This operation was continued for 10 minutes.

(The neck thus obtained is then matured in this last reactor which is maintained at the temperature of 90 ° C. and provided with a stirring which makes it possible to effectively maintain in suspension * the Zeolite during crystallization, after 6 hours the zeclithe is separated from the mother liquors by filtration, washed and dried in an oven at 90 ° C. 140 g of product are obtained, the X-ray diffraction pattern of which is zeclithe A crystallized. between 1.5 and 10 μ with an average diameter of 2.9 μ.

The sequestering power of the Cs ++ ions is 115 mg Ca per gram of anhydrous product and the zeclithe A obtained has the following particle size curve;

Proportion by weight) Diameter (in microns) | 25 2 1.5 Γ '10 1.9! ; 25 2.35; . ; 50 2.9 i:! 75 3.7 i, ί - '· j 30 90 4.6 ‘· 98 6 i · EXAMPLE 2.

- 1_:, The solution of Na aluminate was prepared as before by attacking alumina hydrated with a sodium hydroxide solution and contains 53 g of Al ^ -j and 79 g of Na ^ O per liter ( let>: /,. Λ1 - Ο *., H, Ô ......,. n, i relations, <<. 3 euc f. t>; o cars ce 0, /. 0 ßt / „ *) f '.' pO Na20; , La silicate solution B was preoaret * v. . . ,. , “From: a silica known as ex HoSiF ^ which has the advantage of P ^ -.,; X b n - u ‘-‘- Xg of a very low cost since it is about * A residue of an aiel-î ^ ..! K: brication of aluminum fluoride. This silica. tr ^ q.

; can be easily attacked by a solution of NaOH at 10 ° C. and makes it possible to obtain a solution of this silicate of La rente-- - x 127 * 9 g of Si02 and 37 * 8 g of Na2O su liter (be ratios>; Si02 H20 i and ---— respectively 3.5 and SB).

._! Na ^ D LopO

10 G, TB 1 of solution A and 0.313 1 of solution 3 ç-r.4. x 1 “wwllu ÎÏSj, -.

very according to the procedure described in Example 1. The final A obtained has a sequestering power of 111 me of anhydrous product and a particle size between 3 e ~ 15 μ 1 with an average diameter of 6 P: • i 15 Proportion { £ in weight) Diameter (in microns) 2 4 10 5 | ; ; j ‘25 6 j 50 7.2 ^! 20 75 B, 8 90 10.5: 90 15 j EXAMPLE 3. j i

Na aluminate solution A consists of a so-called "clear 1st washer" solution taken from an alumina manufacturing unit according to the Bayer method and contains 59 g of Al-10 and 62.1 g of Na ~ Ü per liter (i.e. ratios ^ 2 ^ 3 and H20 respectively of 0.58 and 56) * Na20

Na2D

The Na silicate solution B is obtained by dissolving Na powdered industrial silicate in water and contains 137 9 of SiO 2 and 40 g of Na 2 O per liter (ie SiO 2, H 2 O ratios and —— “Respectively 3.5 and 82).

Na20 Na20 / _, 1 'ί 1 »270 1 ct solution A and 0.410 1 do s fs lut 5. on B (which ct.v ;; - et-poc.db un; · :. t du if.élange -final reaction of "5iD2; j 0.6) are treated according to the procedure described in 1 * example 1" l The final zeolite A obtained has a sequestering power of 120 mg; -J- * - 5 Ca ** per seeds of anhydrous product and a particle size between 2 and 8 P with a die:, '. Read mean of 4.8 P:

PjTDqp ^ icn (f by weight) Diameter (in microns) 2 2.6 Î0 3.3 1.0 25 4 -j 50 4.7? ‘75 6 90 7 ί 96 9;

II 15 LXO-TLE. 4 ":

Solution A of Na aluminates is formed from! d * a solution called ^ decomposed liquor * 1 taken from an alurnine manufacturing unit according to the Bayer process, containing 9B, 3 gd d and 165.5 g of liter (either ratios ^ 2 ^ 3 d I: H20 Ka2 ° 20 and “” * respectively 0.36 and 21), retreaded in Alo0 „by addi-! , Na20 ~ ά 0 d, tion of alumina hydrated at 100 ° C and diluted to arrive at a com- [| i final position of 56.5 g of Al203 and 66.4 g of Na2D per liter; I, (be ratios ^ 2 ^ * 3 and respective of 0.53 and 52), if il- Na90 Nao0 i i I i i ^ 2 j. j Solution B of Na silicate is identical to that described in · 25: ’1 * example 3.

i i; 1.220 1 of solution A and 0.430 1 of solution B (which j! Corresponds to a ratio ^^ 2 ^ 3 of the final reaction mixture of il! - Si02! J 0.8) are treated according to the procedure described in Example 1 ,! The final zeolite A obtained has a sequestering power of 120 mg 30 Ca ++ per gram of anhydrous product and a particle size between 2 and 10 P with an average diameter of 4.7 P:

i u

i <Ί ’· _ i * • i fé -π weight), Diameter (in r ^ u-s) 2 2.6 10 3.3 i 25 '4!

5 50 4.7 I

K 6 90 7 90 5 EXAMPLE 5. '10 Solution A has been prepared identified given donations 1 * example 1 from hydrated alumina and sodium hydroxide solution and rcn ~ term o5 g / 1 d' / tL ^ e “G / l of Ls 0 (scient of ratios' ai2d3 h2o and -“ * - * - respectively 0.43 and 63).

Ns-jO Na ~ C

*!

ci & Dj.Iî wiOi: Xi ci & px'CïpBx ^ S pc; X * dzLSSoXuÎ-iün CÎsnS i ® t "Ξ? U

15 of industrial sodium silicate and contains 138 g / l of SiO and 42 g / l of Na2G (being ratios _5 ^ ° 2 and H2 ° respectively

3.4 and 7B). L ^ G f ^ Q

A Na silicoaluminate gel having a!

Al 0 ratio __ 2 .3 _ of 1.1 by sending simultaneously, at temperature

SiG2. ; 20 of 90 ° C., 127 l of solution A and 27 l of solution B, in a reactor of the type described above and the volume of which has been calculated! • »to obtain an average residence time of 4 minutes. The gel as well! , prepared is transferred by overflow into the ripening reactor: - sement .. This operation was continued for 90 minutes. '25 The gel thus obtained is then matured! after 6 hours of ripening at 90 ° C and with stirring, the zeoli-; the is filtered, washed and dried.

; ! 11 kg of zeolite A are obtained having a dry power - i i * jl "p. i have 120 mg of Ca 'per g of anhydrous product and a particle size of 30' between 1.5 and 15 μ with an average diameter of 3 μ! 'i L ~.

t »_______________ ____- I i!. Ρϊ'Γ'ρπιΜ -. 'Cn ('; "en ·> η'dt?) · {En nr * cecns) - 2 .............. i";: 10 1.5 ii 25 '2 d I 5 50 2.8:! 75 3.8 d; 90 5

I 90 T

% j ¥ j; i ,! * l i ‘t *; * j | here! ! <i; i; ! ! *! i j 1 "!; t 'r':; -! ! :> j! , ..........................................

Claims (8)

1. Process for the semi-continuous preparation of reolith A of c-ja- | constant and homogeneous tity, consisting of mixing a sodium aluminate solution and a sodium silicate solution, characterized by the instantaneous and continuous mixing of these two sc-5 lutions in a container in which the average residence time is * between 30 seconds and 20 minutes to form a sky which * crystallization * is carried out subsequently discontinuously. * 2) Zeolithe A prepared according to the method of claim 1, having a tight particle size distribution, 95 £ of the 1C grains being in a range of 2 to 10 μ, and having a higher Ca '' sequestering power or equal to 110 mg Ca per gram of anhydrous product. i 3. The method of claim 1 wherein the aluminite solution is taken from an alumina production plant. | 15 4) Method according to one of claims 1 or 3 wherein the solution of aluminate is saturated with alumina at atmospheric pressure. ; '' I ; ! 5) Method according to claim 1 wherein the silicate solution J ‘:"> i; sodium is prepared from industrial sodium silicates *, jr "I ; 6) Method according to claim 1 wherein the sodium silicate solution 20. is prepared from silica recovered from fluc- • [... . srlicique. ; ! î; J 7) Method according to claim 1 wherein the silicate solution i i! of sodium is prepared from residual silica obtained during! i; wet acid treatment of natural silicoaluminates. t · 1! * 25 8) The method of claim 1 wherein the sodium silicate solution is prepared from silica obtained thermally, for example during the manufacture of magnesium, silicon-metal, or silicon alloys. \ i \ \ \ \ \ v